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Re: Yr 7 Crystallisation Prac
Posted: 13 Oct 2008, 10:30
by Robdean
Thanks for the recipe Rita! Have shown it to one of my teachers and already she has ordered it for Yr 7 for tomorrow morning. We're looking forward to the crystals!
Re: Yr 7 Crystallisation Prac
Posted: 14 Oct 2008, 11:10
by lizzieb
Rita - I got your fax this morning - it'll be very useful.
Many Thanks
Re: Yr 7 Crystallisation Prac
Posted: 03 Nov 2008, 14:01
by lizzieb
Bunnings sell 1k Borax for $6.98 - has anyone found a cheaper source?
Re: Yr 7 Crystallisation Prac
Posted: 04 Nov 2008, 08:21
by sunray18
I just grew the most beautiful Borax crystal star - have to SHOW the staff something knew or they just go into automatic mode!
Sweeeeeeeeeet.....
Re: Yr 7 Crystallisation Prac
Posted: 03 Jun 2009, 10:12
by KarenN
Hi all,
just reading the posts of crystals with alum. Can someone please advise "recipe" for saturated alum solution used for making crystals ?
(or do you just give students alum powder and they make their own solution ??)
Thanks in advance for help, Karen
Re: Yr 7 Crystallisation Prac
Posted: 03 Jun 2009, 11:03
by cecmel
A few years back, I got sick of the solid mass at the bottom of the beakers that resulted when kids made saturated solutions by just adding spoonful after spoonful of alum to boiling water, so I did a bit of checking and measuring.
Results: Solubility of alum (anhydrous): 1g/20ml in cold water, 14g/100ml at 20 degrees C.
3 slightly heaped teaspoons alum is approx 15g.
So if the teacher controls the handout of alum, there's a pretty good chance of getting some decent crystals. We make the original solution - 3 teasp alum, 100ml water - in 250ml beakers, then transfer it to baby food jars. They hold about 100ml, and it means the beakers aren't tied up for however long they decide to grow the crystals.
Cecilia
Re: Yr 7 Crystallisation Prac
Posted: 03 Jun 2009, 11:34
by KarenN
Hi Cecilia,
thanks for the info !
Karen
Re: Yr 7 Crystallisation Prac
Posted: 03 Jun 2009, 12:03
by RosalieM
What a great idea to use baby food jars!! I'll start collecting them for next year's crystal making efforts...
Re: Yr 7 Crystallisation Prac
Posted: 03 Jun 2009, 12:17
by smeee
A Demo to show how crystals form.
Add a spoonful of salicylic acid to about 50mls of methylated spirits.
Store in a dropper bottle and shake well.
Heat up OHP until very warm then place an OHP sheet on top.
In the middle of the sheet add a few drops of the salicylic acid/metho mix and watch the crystals form before your eyes !...from small crystals to larger ( slower cooling )
You can add a drop of food colour to the solution for "effect"
The hotter the OHP the better and faster crystals cool.
Re: Yr 7 Crystallisation Prac
Posted: 03 Jun 2009, 12:20
by Labbie
What a really great idea. Thank you for that tip.